I have spent a heap of time looking myself.
The best thing I have found so far is a PHP calendar from Comdev.com
It has a full demo and admin console which will refresh each hour and that allows you to play with the on line demo. I have extensively tested it and it is easy to use and has pretty much all you need for a calendar. We will use it for a sailing club to show racing and Hall hires.
It is a stand alone PHP package but does need Zend and IonCube plug ins loaded on yr ISP server side. GoDaddy does allow both. It is not available in WordPress but I can’t see what you couldn’t plug it in on a page.
